An open-source implemention of acoustic scattering problems through rigid-porous media in steady laminar flow

  • Nayak, Ashwin Sadanand (MPI Magdeburg)
  • Prieto, Andrés (University of ACoruña)
  • Fernández-Comesaña, Daniel (Microflown Technologies)

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Outdoor acoustic equipment utilize porous layers to isolate wind-noise and ensure quality measurements. Designing effective transducers require prototyping geometrical and material properties alongside environmental conditions. A computational model with an open-source workflow is sought to solve acoustic scattering problems on exterior geometries in presence of laminar flow and porous media. Acoustic propagation over flow is modeled using an Arbitrary Lagrangian-Eulerian (ALE) approach which offers versatility between the choice of underlying Eulerian flow models and acoustic models as Lagrangian perturbations. Steady laminar flow is considered over the exterior of the structure and coupled with Darcy-Forchheimer flow within the porous domain. A finite-volume discretization is utilized to solve the coupled flow problem for compatible boundary conditions. Modeling acoustic perturbations over an arbitrary mean flow is handled using the Galbrun's equations while similar models are amiss for porous media. A novel Galbrun-like model is derived for sound propagating in rigid-porous materials with Darcy-Forchheimer flow. Open-boundaries are handled through perfectly-matched layers (PML) and a finite-element discretization is used with regularizations to enforce stability. The entire workflow is implemented using reproducible open-source software. The popular Gmsh library is used to generate complex meshes; the OpenFOAM solver is utilized to compute the steady flow solution between the coupled fluid-porous domains, and subsequently interfaced with finite-element implementation expressed using the FEniCS library, while the reproducibility of the code is ascertained through containerization. An implementation is demonstrated to study the influence of porous layers on a particle-velocity sound sensor, the Microflown.